1. Field of the Invention
This invention relates to protective envelopes and, particularly, to magnetic recording disk jackets.
2. Description of the Prior Art
A flexible magnetic disk jacket encloses and protects a magnetic recording disk and is inserted along with the disk into a so-called disk drive which is connected to a computer system. The disk drive includes a read/write magnetic head which contacts the magnetic disk through openings in the jacket and either magnetically records onto the disk information supplied by the computer system or magnetically reads information from the disk and supplies such information to the computer system.
Recently, with the advent of small and relatively inexpensive home computer systems, a large market has been developed for prerecorded information or computer programs ("software") which may be read directly by the computer system rather than entered manually by the user. Such software is relatively expensive and easily duplicated and has given rise to an illicit market specializing in the unauthorized duplication and sale thereof. It is, therefore, necessary that users, distributors and manufacturers be provided with means for distinguishing authorized and illicitly produced software.
The present industry-accepted method of manufacturing a disk jacket is disclosed in U.S. Pat. No. 4,038,693 issued to Huffine et al. and U.S. Pat. No. 4,263,624 issued to Chenoweth et al. These patents disclose a disk jacket formed from a rectangular, perimeter cut sheet which includes three envelope-type flaps extending from the three edges of one-half of the rectangular sheet. The center line of the sheet is heated and folded to define top and bottom panels of the jacket and the two flaps adjacent this fold are in turn folded over the bottom panel and secured by an adhesive, thermal bonding or ultrasonic welding to form a pocket between the two panels. The magnetic disk is inserted into this pocket and the flap opposite the initial center-line fold is folded over and likewise secured to contain and protect the magnetic disk and form a completed jacket.
These jackets are available from manufacturers in a partially assembled form wherein all that needs be done to complete the assembly is insert the disk and fold and secure the final flap. Since the information recorded on a disk is easily duplicated onto another disk, illicit producers need only insert a duplicated disk into a partially assembled jacket and secure the final flap to produce a software package which is indistinguishable from an authorized package.
Alternative disk jacket constructions have been proposed by U.S. Pat. No. 3,864,755 which depicts a disk jacket having a relatively rigid, flat back cover and a relatively thin front cover which is thermoformed to accept the disk and bonded to the flat back cover and U.S. Pat. No. 3,668,658 in which the jacket is a composite of three sheets which include a central gasket layer surrounding the magnetic disk and adhesively attached to flat side panels.